1. Field of the Invention
The present invention relates to a dispersing apparatus for stirring and dispersing a liquid compound or semi-liquid compound with dispersing media (hereinafter referred to as “media”) such as zirconium balls, glass beads, ceramic beads, steel balls and the like, and more particularly, to a dispersing apparatus for dispersing that blend through the shear force generated by passing the compound as a dispersing target through a vessel that is a basket-shaped container wherein the above media are charged and stirred.
In the present specification, a “compound” means a mixture of two or more kinds of materials, and “dispersing” includes stirring or mixing.
2. Description of the Prior Art
In the manufacture of compositions containing solid materials, for example, dispersion of these solid materials into elemental substances of respective particles is performed in the manufacture of paints, inks, and medicines, and the other manufacturing fields of various goods.
For example, the manufacturing of a composition containing solid materials such as paint, ink and the like is made through a premixing process for mixing resin varnish with pigments and obtaining paste. A dispersing process for dispersing the paste obtained in the above premixing process involves the use of a dispersing apparatus, whereby obtaining mill base pigments are dispersed uniformly in the resin varnish, and a dissolution process wherein the mill base obtained in the above dispersing process is mixed and dissolved with solvent, resin varnish and additives as needed by use of a dissolver or the like.
In the case when secondary particles formed by condensing elemental substances of non-dispersed particles such as pigments or the like are formed in manufactured paint or so, the application surface to be obtained by application of such a paint becomes rough and unattractive. Accordingly, the dispersing process in the above process is performed in order to disperse the secondary particles of pigment particles remaining in the paste obtained in the premixing process into the elemental substance particles at nano level.
In such a dispersing process, in order to carry out dispersion more efficiently, a sand grind mill is used as a dispersing apparatus using media, that can continuously disperse the paste obtained from the premixing process.
This sand grind mill, as shown in FIG. 7, is equipped with a vertical vessel 2 wherein for example glass beads with a diameter of about 1 to 2 mm as media are charged, and a shaft 3 that rotates in the vessel 2, and the above stirrer shaft 3 is provided with discus-shaped disks 50 protruding in the outer peripheral direction of the stirrer shaft at specified intervals.
At the lower end of the above vessel 2 a guide inlet 24 is provided for guiding the paste obtained in the premixing process into the vessel 2, while at the upper portion of the vessel 2 a discharge outlet 25 is provided for discharging mill base whose dispersion is completed, and is further provided with a separation means 26 reborn by a screen or the like for separating media from the mill base discharged from this discharge outlet 25.
Further, in the sand grind mill shown in FIG. 7, the outer circumference of the vessel 2 is surrounded with a jacket 5 via specified space, and a flow route 51 of a cooling medium is formed in the space formed between the outer wall surface of the vessel 2 and the inner wall surface of the jacket 5, and a cooling media such as cool water or is guided into the flow route 51, whereby the heat produced at the moment of dispersion can be cooled by heat exchange with the above cooling medium.
In the sand grind mill comprised as mentioned above, when the stirrer shaft 3 is rotated in the vessel 2, media are stirred at high speed in the vessel 2 by the rotation action of the disk 50 being provided with the stirrer shaft 3, and the paste guided from the guide inlet 24 is dispersed by the shearing power of the above media.
The mill base obtained by dispersion of the paste as mentioned above moves upward in the inside of the vessel 2, and is discharged from discharge outlet 25, after media is separated through a screen 26, and is sent to following processes such as a melting process and so on.
Further, as an improved type of the above sand grind mill, there is a sand grind mill provided with the vessel horizontal, wherein pin-shaped projections are being provided with the disk surface so as to enhance throughput. (Refer to Japanese Patent KOKAI (LOPI) No. 2001-120976.)
Moreover, in an example of another dispersing apparatus using media, as shown in FIG. 8, stirrer pins 50′ are attached onto the end of a stirrer shaft 3 that is rotated by a driving source such as a motor or the like, and the periphery of the stirrer pins 50′ is surrounded by a basket-shaped vessel 2 wherein holes 7 such as small holes or slits are formed on at least the side wall thereof, whereby comprising a dispersing apparatus 1, and media are charged into the vessel 2 of the dispersing apparatus 1, then the media are stirred by rotating the stirrer pins 50′ in the vessel 2 when submerged in a compound filling the tank 8. Large particles of the solid materials in the above compound are broken into further finer particles by the shearing power produced by the media stirred in the above vessel 2, and pigment particles that are made into further finer particles flow out from the holes 7 prepared in the side wall or the like of the vessel 2, and are circulated by convection in the tank 8 and flow through guide inlet 24′ opened at the top of the vessel 2 into the vessel 2 again, and are dispersed by breaking into still further finer particles. (Refer to U.S. Pat. No. 5,447,372 and Japanese Patent KOKAI (LOPI) No. 2000-350930.)
The dispersing apparatus disclosed in the above 2000-350930 has the benefit that the above dispersing process and dissolution process can be performed simultaneously, and these dispersing apparatuses are used selectively according to applications.
Among the above dispersing apparatuses shown in the prior art, in the dispersing apparatus shown in FIG. 7, namely, in the sand grind mill, it can be used in the dispersing process for dispersing the paste obtained in the premixing process and obtaining a mill base wherein pigments are dispersed uniformly in resin varnish. However, in order to obtain a final product such as a paint from the mill base obtained as mentioned above, it is necessary to go through a dissolution process wherein the mill base obtained in the above dispersing process is mixed and dissolved with a solvent, resin varnish and additives as needed by use of a dissolver or the like.
On the other hand, in the batch-type dispersing apparatus shown in FIG. 8, the paste obtained in the premixing process can be dispersed and dissolved with a solvent, resin varnish, additives and the like, therefore, it has an advantage that the dispersing process by the above sand grind mill, and the dissolution process can be performed in a single process simultaneously. However, because the compound in the tank as the object of the dispersing process is to be guided into the vessel by the convection produced in the tank, the processing time thereof appears to be long in comparison with the sand grind mill wherein a compound is forcibly guided into the vessel by use of a pump or the like.
In such a batch-type dispersing apparatus, if the throughput thereof is to be improved, the rotation speed of pins 50′ may be accelerated, but for that purpose, it is necessary to make the driving source such as a motor or the like that rotates the stirrer shaft 3 larger in order to generate a high output. Moreover, it is also necessary to make the transmission mechanism for transmitting driving force, and the stirrer shaft 3, pins 50′ stronger in order to operate under the high driving output. Thus, there are limits in improvement for high speed processing.
Moreover, in the batch-type dispersing apparatus, because comparatively large particles in a compound filling the tank 8 tend to collect at the bottom of the tank 8, in order to circulate those particles that tend to collect on the bottom of the tank 8 and to guide them into the vessel 2, it is necessary to provide vanes for flowing fluid 9 for generating a flow of the compound in the tank 8 in the outside of the vessel 2, and also to prepare stirrer shafts, driving sources and the like for rotating these vanes for flowing fluid 9. Therefore, in this kind of dispersing apparatus, the structure thereof becomes comparatively complicated.
Furthermore, in the dispersing apparatus of the above structure, particles in a compound are likely to collect in vessel 2 most likely under the vessel 2 in the tank 8, while in the dispersing apparatus of the structure shown in FIG. 8, the vanes for flowing fluid 9 cannot be provided under the vessel 2, whereby making it difficult to sufficiently stir the contents of the tank 8 under the vessel 2.
In order to solve the above problem, for example, the lower end of the stirrer shaft 3 inserted into the vessel 2 may be expanded downward through the bottom plate 22 of the vessel 2, and the vanes for flowing fluid 9 may be provided on the lower end of the above stirrer shaft. However, in such a structure, with some kinds of media, fragments of media and the like crushed during stirring get in a space or gap between a shaft hole formed in the bottom plate 22 of the vessel 2 and the stirrer shaft 3 whereby being defaced, shortening the service life of the bottom plate 22 of the vessel 2 and the stirrer shaft 3.
Further, in both the sand grind mill in the prior art described above and the batch type apparatus shown in FIG. 8, in the dispersing apparatus wherein dispersing of media is made by the disks 50 provided on the stirrer shaft 3, the plate-shaped disks 50 have small resistance at the moment of contacting media. This is because the power to stir media provided only by the vanes 50′ is weak and consequently the shearing power produced by stirring of the media should be weak.
Moreover, although media are comparatively easily stirred around the disks 50, because intervals around 100 mm are generally prepared between each one of the disks 50, the media at the intervals of each one of the above disks 50 are difficult to stir. Therefore, not all the space in the vessel 2 is used effectively for dispersion, and as a result, the dispersing efficiency thereof is not preferable.
As mentioned above, the problems that the sand grind mill has occur in same ways when adopting the same structure in the batch-type dispersing apparatus show in FIG. 8. Moreover, as shown in the above 2001-120976, even if pin-shaped protrusions are provided on the disks, although the stirring property of the media around the portions where the pin-shaped protrusions is improved, it cannot be denied that portions that cannot be used effectively for stirring media in other portions still exist. Therefore, the above problems cannot completely be solved.
On the other hand, apart from the disks 50 mentioned above, in the dispersing apparatus wherein media are stirred by vanes 50′ being provided with the stirrer shaft 3, media that collide with the rotating vanes 50′ can be flipped off in the rotation outer peripheral direction, whereby media can be stirred.
However, although media can be flipped in this manner by their collision with the vanes 50′, the movement direction of the above media is constant in the direction of the circumference, and the shearing power is weak.
Moreover, because the moving speed of the roots (toward the stirrer shaft side) of the vanes 50′ is slower than that of the ends (toward the vessel side) of the vanes 50′, the shearing power produced at the root portions of the vanes 50′ is weaker than that at the end portions thereof.
For this reason, it has the problem that there is unevenness in conditions after dispersion between the compound that is dispersed by passing through the portion around the center of the vessel 2 and the compound that is dispersed by passing through the portion near the wall surface of the vessel 2.
The present invention has been made to solve the above problems in the prior art. Accordingly, an object of the present invention is to provide a batch-type dispersing apparatus wherein a basket-shaped vessel is submerged in a tank filled with a compound, and media charged in the vessel is stirred by stirrer vanes, whereby particles in the compound are dispersed, and the above dispersing apparatus can improve stirring capability without accelerating the rotation speed of the stirrer vanes.
Moreover, another object of the present invention is to provide a dispersing apparatus using the above vessel that prevents particles in the compound from piling up under the vessel in the tank by use of a comparatively simple structure.
Furthermore, still another object of the present invention is to provide a dispersing apparatus that can stir uniformly the media charged in the vessel, and accordingly can use the entire space of the vessel for dispersion, and can have high dispersing efficiency by stirring components thereby increasing the shearing power produced by stirring of media, and accordingly can be made into a smaller size than the dispersing apparatus according to the prior art, and can perform quality constant dispersion with high dispersing efficiency.